Pilot valve



March 4, 1958 R. c. DU BOIS I 2,825,354

PILOT VALVE Filed March 16, 1954 F I G. l

1 K r g M l v I mg l6 o qi l7 l2- l9 ll 9 F l G. 2

25a INVENTOR.

Robert Clark Du Bois ATTO R N EY.

United StatesPatent PILOT VALVE 7 Application March 16, 1954, Serial No. 416,453

8Claims. Cl. 137-85) 7 The general object of the present invention is to provide an improved pilot valve suitable for use in a pneumatic balance system.

A more specific object of the present invention is to provide a new'and improved pilot valve which is characterized by its use of a single diaphragm unit and a double acting valve member to achieve accurate reproduction of a control pressure.

The present invention is to provide a pilot valve which includes a feedback and pressure transmitting chamber, a regulable inlet for fluid under pressure and a control or nozzle pressure chamber separated from the first mentioned chamber by a flexible diaphragm. Also included is 'a flexible exhaust conduit within one of said chambers operative to reduce the pressure in the feedback chamber following an increase in the pressure in that chamber relative to the pressure in said nozzle chamber.

' The invention is thus adapted for use in pneumatic balance systems heretofore including two diaphragms, such for example, as the systems shown in the Moore Patent 2,125,081 of July 26, 1953, and in the Johnson Patent 2,6l8,286 of November 18, 1952.

The use in the present invention of a single diaphragm, the double acting valve, and the cooperating flexible exhaust conduit permits a much simplified form of pneumatic relay thus enhancing its ease of manufacture and making the relay comparatively inexpensive without any accompanying loss of sensitivity or accuracy.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. Fora better understanding of the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matterin which I have illustrated and described preferred embodiments of the invention.

In the drawings:

Fig. l is a sectional elevation of a pilot valve;

Fig. 2 is a sectional elevation of a modified form of pilot valve; and

Fig. 3 is a diagrammatic showing of a portion of a control system including the pilot valve shown in Fig. 1.

Unless otherwise noted corresponding components shown in the various figures carry corresponding reference characters.

Fig. 1 illustrates achambered pilot valve casing structure 1 which encloses a supply chamber 2, a feedback andpressure transmitting chamber 3, and a control or pressure chamber 4 which regulates the pressure in the chamber 3. :As a matter of convenience, it is assumed in the description of the structure 1 shown in Figs. 1 and 3, that the feedback and transmitting chamber 3 is beneath the supply chamber 2 and above the nozzle pressure chamber 4. In fact, however, the general operation of thepilot valve shown in Fig. 1 is independent ofthe spatial position of the pilot valve structure. As shown, the casing structure comprises two rigid cupshaped sections Sand 6 with outwardly extending periphan flanges "Tend 8"at their adjacent open ends. The

2,825,354 Patented 1 flanges 7 and 8 are secured in abutting relation by clamping bolts 9.

The feedback and transmitting chamber 3 and nozzle pressure chamber 4 are separated by a diaphragm which in the preferred form shown in Fig. 1, comprises a rigid central portion 10 and a surrounding flexible, non-elastic annular portion 11 which has an inner edge portion clamped against an outer portion of the diaphragm part 10. The peripheral or outer edge of the annular diaphragm portion 11 is clamped between the casing flanges 7 and 8 by the bolts 9. The diaphragm section '11 may advantageously be made of leather, rubber or plastic material which is flexible and has no significant elas ticity. The diaphragm may also be made of thin flexible metal corrugated so as to make its resistance to the transverse movement of the central portion of the diaphragm quite small.

The rigid central portion 10 of the diaphragm is formed with a transverse central port 12. The lower end of the port 12 receives an upper end portion 14 of a flexible, substantially non-elastic, exhaust tube 13 which has its outer end 15 extending through and am chored in an opening in the annular body portion of the casiu member 6. The upper end wall of the casing section 5 is formed with a central port 16 in alignment with the port 12. The flow of air under pressure into the chamber 3 through the port 16 and the flow of air out of the chamber 3 through the port 12 and tube 13, are each regulated by valve means 17. As shown, the valve means 17 comprises a stemportion connecting upper and lower plug valve sections 18 and 19, shown as tapered and having their larger upper ends of larger diameter than the stem portion. The valve member 17 is biased by a spring 26 for movement in the direction in which its valve portions 18 and 19 close the ports 16 and 12, respectively. Although not shown in the drawing, it may be desirable in some uses of this pilot valve to retain this valve member 17 in a partially opened position rather than in the closed position shown. As, shown in Fig. 1, the spring 20 is in the form of a tapered helix with its larger upper end engaging the top wall of the member 5 and its lower end engaging the upper end portion of the valve member 19. Although not shownin the drawing, any standard screw actuated cap means may be used to alter the spring bias on the valve 17 if such :is desired. I

'Air at; a constant supply pressure, which may well be 20 p. s. i., is supplied to the chamber 2 through asupply pipe 21. The pressure in the chamber 3 is transmitted to a bellows chamber 26 or other control element byv a pipe'22. Such other control apparatus might well be the head of a control valve as disclosed in the previously mentioned Johnson Patent 2,618,286. A pipe 23 may transmit the pressure to chamber 4 from a bleed nozzle 25 such as is shown in Fig. 3 or from some other analo-- gous control element. 4 a. I. I By way of example, I have illustrated the use of the pilot valve 1 in a control system' shown in Fig. 3; in"

which the bleed nozzle 25is connected by a pipe 23 to the.

control pressure chamber 4, andis connected through-a restricted orifice 25a to the air supply pipe 21. In Fig.3, the feedback pressure variations in the chamberA and thereby change in "the magnitude "of the input force" F Plfl md pipe 22 is connected to the fixed end of the control chamber 26 which has its movable .end 27 in snrss qre in hamb r? te -thefleyier 28 cause the control pressure being transmuted. b P ne 231mm cont n es u e h mb 4 to be changed. As the force ;F is gradually increased the pressure in chamber 4'will also be increased and if this o c i ;F :i -idiec ica d a c rr spo ding rease in the control pressure chamber 4 will likewise take place? 7 ymnthe pccurrence of an increase in the aforementioned force in Fig. 3i-ithei beam 2 8 will move to a position 7 e that is closer-to the nozzle 25.; This action will causerthe' level 'ofthe fluid pressure in the portion of the'conduit 23 that is above the restriction 25 1 to increase. This increase in {fluid pressure -will,in turn, be transmitted by conduit}?! to the control pressure chamber 4. Ifit is the spring 20. V This action will permit'air at a predetermined constant supply pressure; being transmitted by the I 7 conduit 21,10 flow from'a supply chamber 2 through the port:-16.into the feedback and transmitting chamber 3;

7 If the level of'the pressure in the chamber 3 is of a'lowier in'an upward direction from the pseated position valvein the fiow lin'e notshown; I

. ingrtwo associated. diaphragms as is shown for example;

n F 9f the drawin -M v V The size of the enclosed areas of the chambers sand 4 may be so proportioned as to provide a still'more rapid means ,of transmitting changes in nozzle pressurewthroughf thelrelay valve and conduit; 22A to a control elementf such as the head ofia control, valve inia'tflow line, not I shown. It should' also"furthcr'benoted that the tapered valve 17 is biased by the spring 2 0'to, close the di giend 14 of the exhaust tube 13 when the upperport onm 7' of the valve 17 is still permitting evena small, predeter-f:

It canth'us be seen that'th'e relay 1 will'thus provide a means for speeding'up the response wtirnet-that' is norrnall y" requirediby a bleed nozzle chamber and feedback bellows connected therewith to transmit a change in nozzle pres; I si Y sure to the-ahead of ra control element such as'arcohtrol.

The pilot valve 1 shown in'F'g's; l and 3is character- 1' izedbyiits'iuse ,ofa' single diaphragmtoaserve control; a purposes heretofore served by a pilot. valveistructure havin the-previously mentioned prior Patentsi2il 25,08 lf andl valuesthan the level of the aforementioned regulated supply pressure that is permitted to flow into'this cham-- her 3;.thr m 1ghrthesp c'irt 16: the pressure of the fluidiin chamber: 3 will be then increased by an amount that'is equal'to thelevel of the pressure in the no zglel 25ror is directly proportional to' the increasein the force Fithat, a was applied to movethe beam'28' closer totheinozz'lei 25. This increasegin fluid pressure level will then be trans{ mitted 'byrway oflthe'conduit 22 to the'interi or ofthe' '28'to move' in ai'direction'away from the nozzle and a sli'ghtly'in a downward direction from the positionshown in Fig, 1.' The level of the timid pressure in chamber 3 will then be lowered due to the fact'that there is now'a bleed" to jatmosphere .from this chamber-between the" lower-portion 19 of the valve'17 andport 12 ithrough the exhaust tube 1 4, '13, 15. As the lowering of'ithe level a of this pressure continues, apoint will .be reachedwherelij it the le'vel'of'thepressiirelin chamber 3 will startto drop 1' below the level of the pressure in the chamber 4,: As'this '"condi tion occurs the fluid pressure acting on the diae;

phragm11 in the chamber, 4will then be permitted to move the diaphragmi n an upwardtdirection so that the a ing fromnth'ei spirit o my inyeenrtigmas xsertnufgrrth exhaustport 12 connected to the atmosphericexhaust tuber 13; 14, s will be closed byr the valve 19.; If t e lowering-of the level of the-.fluid pressure in the chamber 7 3ucoiitiniies thenlthe ak/e 17 willbec aus'ed to move inj an u and direction from" th'ejeated position. show rt in" an 'thus' beseenlthat as the; inputfforce E m'oves thel tQwdrclsthe no'zzle'fthis force will simultaneouslybej sedi a torc es createdTby the; feedback and j transi a a cnduit 22 and bellowsi26 V'V L V V" V:: 'V70 q 'nngibmh omp s on";

sprin'gjjl, shown in; Fig; 1, it "is possible to govern Ethe n 7 7' V will bpehiort 16; i-

;m a inanner similar to that previously described ssure atlwh'ich thefvalve 17 feedbackbellowschamber 26 so that 'a force ac ting in the. opposite direction to the force Elmay be applied ;to i

I'rebalance the b'eani'28. This aetion willcausetheflbeam i 40 a greater amount of fluidin-the chamber '4 to. be: bled throughthe conduit'23 and nozzle 25to 'the'atmosphere a snrrounding the casing 1. (Thishfluid bleeding actionwill a .i id to ca'use'ithe level of the pressure .of the fluid in.

chamber 4fto drop,;the valve 17 to close the'port 16'and the rigid central portion'lo of the' diaphragmill to move 2,618,286. The use of a'single diaphragminj'a pilot v lve; 7-

1togserv e operating purposes heretofore requiringflthe use 1 a of two pilotyalve diaphra'gms, is -made possible by appli cants use of'the tube was a flexible exhaust tube reignlatingsthe pressure'in the chamber-3 1 a 7 I Fig. 2illust ratesan embodimentof-theinventionshownl" V in Fig. 1,' which differs structurally rfrom the apparatus; shown in Fig. 1 in; that it corriprises elementsfiqrflfla',

7 12a, 13a,r 15g',;17A, 181 191; andQZOa which are generallyi- 'lilre, but difler somewhat,fromtheuprqviously mentioned 7 e ement 5 .0, 1 1 ,17, 9 ahd The d e ences just jeferred to are relativelyimimpo; n t frohi the operating iviewpoinnl Itv is tojbe noted,'.however that in FigjZ, the pipe llia iis located in the c am e s V instead; ofin the chamber 4 :as shown injFigi'l, In Fig '2 the exhaust port12a is formedgwholly'withinithe tcentral j i aph xn -rpor iofl l a d'Comprises an upper poriiph'- coaxialiwi th the casing structure, and aflower, portion 1 12a transverse to the portion 12d. Thetube 13a in' Fig',"

2 is shown ashavi ng one end'anchoredin thediaphragm portion 10a with its boreinregister with'thefdischarge end of the -passages portion 12a ',.fThe discharge: em 7 portion of the exhaust pipe 13a extends through 'd' is" anchored in thecylindrical.portion'5;of'thefupper casing f section ofithe 'pilot valveshow'n in Fig. 2. 1 As will be; i 1

v apparent;thepilotvalveshowninfFigJZ'may eitherfbe i I i incorporatedin a pneumatic balance systeintoi the ty e 7 shown in'Fig 3 or asp substitute for thel double'diaphragrn V I I ave-illustrated anddescribedithebe'st forms of embpdi I Having nowdescribed 'y invention, what j 'ne w andj d'esire to' secure byi'LettersiPate nt a 1. A'pilot valvej strncture comprisihgji' type'ofreverse acting'relay showninlthe'previoi slyimfilk' While,'iniaccordance with th pijovisionslof statutes,

=inent'of invention nowknownto me, it wil lent to cs r e me' ai h 'c 'l s s b in'thel forms 'of the apparatns.disclosed without:

appended 'claims and"thatiin ome cases certain f s; of'my inventionxm'ay be"used tq advantag without at corresponding useo f othergfeaturese :3; i

a n re o a a fis au gs s rqi ifirs said port into said first chamber and the outflow of fluid through said exhaust conduit, said valve means operating automatically to close said port and said inlet end of said exhaust conduit when said diaphragm occupies an intermediate position and automatically opening said port when said diaphragm is displaced toward said port from said intermediate position and automatically opening said exhaust inlet when said diaphragm is displaced away from said port and intermediate position, and a connection to said second chamber operative to transmit a control pressure from a remotely located control apps ratus to said second chamber.

2. A pilot valve as specified in claim 1, in which said exhaust conduit is formed of flexible, non-elastic material.

3. A pilot valve structure as specified in claim 1, in which said exhaust conduit extends through said diaphragm and thence through a stationary portion of the wall of said second pressure chamber.

4. A pilot valve structure comprising in combination, a casing enclosing separate first and second pressure chambers, a flexible diaphragm interposed between and separating said chambers, means including a port opening into said first chamber for supplying fluid under pressure to that chamber when said port is open, a pressure transmitting conduit having one end in communication with said first chamber, a flexible exhaust conduit having its inlet end extending into said first chamber and having its outlet end opening into the space external of said chamber, valve means controlling the flow of fluid under pressure through said port into said first chamber and the outflow of fluid through said exhaust conduit, said valve means operating automatically to decrease the flow from said port and increase the flow through said exhaust conduit when said diaphragm is displaced in a first direction, and to increase the flow through said port ard decrease the flow through said exhaust when said diaphragm is displaced in the opposite direction, and a connection to said second chamber operative to transmit a control pressure from control apparatus to said second chamber.

5. A single diaphragm valve actuating relay to trans nut a pressure from a casing which varies in accordance with the magnitude of a control pressure comprising, a rigid and a flexible partition within said casing, a supply port in said rigid partition and an exhaust port attached to said flexible partition, a tapered double acting valve having a supply and exhaust port engaging portion for regulating the flow of a supply pressure into and out of the portion between said partitions, a biasing means acting on said valve portions to urge said portions in a direction to close the supply port and exhaust port in said flexible partition, a flexible atmospheric exhaust tube connected at one end to said exhaust port and having its other end connected to an opening in the wall of said casing, means for supplying a control pressure of varying magnitude acting on the face of said flexible partition on the side opposite said rigid partition, said flexible partition acting on said valve to open said supply port upon increase in the magnitude of said control pressure beyond a predetermined amount and said biasing means acting on said valve to restore said valve to its partially open position as the magnitude of said control pressure returns to said predetermined amount, said flexible partition also acting on the valve to close said supply port and open said exhaust port when said control pressure drops below said predetermined amount and acting to reverse this latter action as the control pressure returns to said predetermined amount.

6. A single diaphragm valve actuating relay to transmit a pressure which varies in accordance with the magnitude of a control pressure comprising, a rigid and a flexible partition within a casing, a supply port in said rigid partition and an exhaust port attached to said latter mentioned part of said partition, a tapered double acting valve having a supply and exhaust port engaging portion, a biasing means acting on said valve portions during normal operating conditions to close the exhaust port in said flexible partition when said supply port is in a partially open position, a flexible atmospheric exhaust tube connected to said exhaust port, means for creating a variable control pressure acting on one side of said flexible partition, said flexible partition acting on said valve to further open said supply port upon increase in said variable control pressure beyond a predetermined amount and acting to restore the valve to its partially open position as the said variable control pressure returns to said predetermined amount, said flexible partition acting on the valve to close said supply port and open said exhaust port when said variable control pressure drops below the predetermined amount and acting to reverse this latter action as the variable control pressure returns to said predetermined amount, and a conduit connected to said casing portion between said two partitions for transmitting said pressure between said partitions from said chamber.

7. A pilot relay for producing an outlet pressure which follows an input control pressure by regulating a supply pressure fluid flowing into and an exhaust pressure from a chamber, a conduit for transmitting said outlet pressure, the improvement comprising a flexible member fixedly attached at its periphery to the wall of said chamber and having an aperture in its central portion, a flexible exhaust tube having the outer peripheral portion of one of its ends inserted in and attached to said central portion and having its other end exhausted to atmospheric pressure, a portion of a double acting tapered valve in said chamber biased by a spring means during normal operating conditions to close said diaphragm end of said exhaust tube when a second portion of said valve controlling the said supply pressure flowing into said chamber is in a partially open position, said input control pressure acting on said flexible member, said flexible member acting on said valve to regulate the degree of movement of said valve with respect to said control pressure, said control pressure tending to further open said supply port when said diaphragm is moved toward the valve and tending to close said supply port and open said exhaust tube port when said diaphragm moves in the opposite direction.

8. A pilot valve structure comprising in combination, a casing enclosing separate first and second pressure chambers, a flexible diaphragm interposed between and separating said chambers, means including a port opening into said first chamber for supplying fluid under pressure to that chamber when said port is open, a pressure transmitting conduit having one end in communication with said first chamber, a flexible exhaust conduit contained within said first chamber and having its outlet end communicating through an opening into the space external of said chamber, valve means controlling the flow of fluid under pressure through said port, into said first chamber, and the outflow of fluid through said exhaust conduit, said valve means operating automatically to decrease the flow from said port and increase the flow through said exhaust conduit when said diaphragm is displaced in one direction, and to increase the flow through said port and decrease the flow through said exhaust when said diaphragm is displaced in the opposite direction, and connection to said second chamber operative to transmit a control pressure from a control apparatus to said second chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,332,627 Erbguth Oct. 26, 1943 2,517,051 Swenson Aug. 1, 1950 2,587,404 Stelzer Feb. 26, 1952 2,618,286 Johnson Nov. 18, 1952 

